The invention pertains to permanent magnet devices for separating stacks of sheets of ferrous steel.
BACKGROUND OF THE INVENTION
The use of fanner magnets is well known in the manufacturing arts. Fanner magnets serve to fan out or separate sheets in a stack of metal sheets, thereby facilitating the movement or transfer of sheets utilizing handling devices, such as pickups, suction cups, or other lifting or moving devices. Such magnets operate on the principle of creating repelling polarities among the individual sheets.
There are a wide variety of methods used for separating magnetic sheets. One example is found in U.S. Pat. No. 4,815,916, issued to James A. Beck, and teaching a plurality of magnetic elevator devices disposed along the sides of a vertical stack of magnetizable steel objects, such as sheets. Another type of device is found in U.S. Pat. No. 4,743,006, issued to Fred Bole, Jr., et al., and discloses a fanner magnet assembly including a power-actuated carriage for movement relative to a stack of sheets.
However, prior sheet separators are limited in their operation, and are not particularly well adapted to separating palletized sheets of metal. When placed in pallets, a stack of steel sheets (or sheets of other ferro-magnetic composition) is typically aligned and positioned between pins on a pallet to restrain the lateral movement of the stack of sheets while the pallet is being transported and processed. Typical pallets are equipped with a large number of pallet pins located around the perimeter of the pallet which surround the sheets. These pins are placed in cavities, thereby creating a xe2x80x9cfencexe2x80x9d of pallet pins surrounding the sheets of ferrous material. Pallet pins may be threaded into corresponding threaded cavities in a pallet, or may be mounted using xe2x80x9cbayonetxe2x80x9d type locking whereby the pallet pin is engaged and disengaged relatively quickly from the cavity in a pallet by placing a plurality of pallet pins completely surrounds the steel sheets, the sheets are effectively restrained from movement in relation to the pallet.
In the manufacturing environment, pallets equipped with pallet pins surrounding a stack of metal sheets are transported to the vicinity of an industrial processing machine. Typically, an external-type sheet fanner, which may be magnetic, is positioned close to the pallet to facilitate separation of the upper sheets from the stack. The uppermost sheet is then engaged by either a magnetic or suction-type gripper which will lift the uppermost sheet vertically from the stack, and free from the pallet and associated pins.
Improvements to this process can be realized by utilizing specialized magnetic pallet pins of the type described herein.
The invention is a new type of pallet pin which contains an integral rotating magnet assembly. The integral magnet assembly is mounted within an inner cylindrical cavity of the pin and is attached to an axially extending member which is coaxial with the pin""s circumference. Although the magnet is of approximately the same length as the pin""s cylindrical length, it occupies only a portion of the circumference defined by the interior of the cylinder.
Magnetic pallet pins of this description are substituted for traditional non-magnetic pallet pins in one or more locations around the perimeter of the pallet. The internal magnet assemblies are rotatable within the cylinder, and thereby positioned either away from or adjacent to the sheets of metal carried by the pallet. When the magnets are rotated into a position in proximity to the sheets in the stack, the sheets are temporarily magnetized such that identical magnetic polarity exists at the edges of the sheet proximate to the pallet pin. This causes the sheets to repel one another and separate, thereby facilitating their removal from the stack.